Together with the miniaturization of portable electronics in recent years, integrated semiconductor circuit devices have been required to be mounted with higher density. In order to make this possible, attempts have been made to stack a number of semiconductor chips three-dimensionally.
In three-dimensional integrated semiconductor circuit devices, semiconductor chips are generally connected through micro-bumps so that signals can be exchanged between them. In the case where there are three or more semiconductor chips, however, it is necessary to have through vias that penetrate through the chip(s) in between.
In order to create these, a complex manufacturing process is required, as well as high processing precision.
A method for electrically connecting semiconductor chips through capacitive coupling has also been proposed. In this case also, there are few problems when there are two semiconductor chips but the efficiency of signal transmission is much lower when there are three or more. In order to compensate for this, high power is required, and a problem arises, such that the power consumption increases.
Another method that has been proposed is one for mounting an antenna on a semiconductor chip for communication between chips. In this case also a problem arises, such that the efficiency of transmission is low when there are three or more semiconductor chips.
Because, a multilayer wiring structure is formed by providing interlayer insulating films, such as of oxide or nitride, on a silicon substrate having impurity-doped regions, and therefore the electrical field generated by the antenna passes through regions of different dielectric constants, such as impurity-doped regions, the silicon substrate, the oxide films and the nitride films, in the semiconductor chip.
In the case where an electrical field passes through films having different dielectric constants, there is reflection in the interface, and thus the efficiency of signal transmission is low.
Thus the present inventors proposed magnetic field communication through inductive coupling between chips mounted and stacked using coils formed of wires on the chips of LSI (integrated circuit device) (see for example Patent Documents 1 to 7 and Non-Patent Documents 1 to 8).
Here, the three-dimensional integrated circuit device for a magnetic field communication proposed by the present inventors is described.
FIGS. 11(a) and 11(b) are diagrams illustrating the structure of the coil for magnetic field communication (see for example FIG. 2 in Non-Patent Document 2). FIG. 11(a) is a conceptual perspective diagram, and FIG. 11(b) is a conceptual projection plan diagram.
As shown in the figures, two pairs of rectangular spirals are formed of a metal wire in middle and upper layers which are approximately the same in shape, and the rectangular spirals are alternately connected up and down through vias to form one coil as a whole.
Concretely, if the coil wire is followed from point A, the lower layer metal wire runs out from point A (broken line), connects to the middle layer metal wire through a via (diamond), which makes one round clockwise (dotted line) and connects to the upper layer metal wire through another via (square). The upper layer metal wire makes two rounds clockwise (solid line) and connects to the middle layer metal wire again through yet another via (square), which makes two rounds clockwise (dotted line), connects to the upper layer metal wire again through still another via (square), which makes one round clockwise (solid line) and runs to point B.
Concerning magnetic field communication using this coil, the present inventors examined the cross talk occurring not only in the signal receiving coil facing the transmitting coil but also in the receiving coil adjacent to this receiving coil. They found that when the interval between adjacent coils are set to a certain value, the value gained by integrating the magnetic flux density B within the receiving coils becomes 0; that is to say, cross talk can be prevented (see Patent Document 4).
The present inventors also examined the effects of a peripheral wire on the efficiency of signal transmission when it was provided between such a pair of facing coils (see Non-Patent Document 8). They confirmed that a peripheral wire running in one direction like conventional bus lines barely affect the efficiency of transmission.
Here, in the case of a wiring pattern forming a closed circuit, an eddy current is generated in the peripheral wire due to the magnetic field from the coil, and this eddy current causes the efficiency of transmission to get lower.